1. Field of Invention
The present invention relates to a device for controlling a surface treatment installation, in particular for the automotive industry.
2. Description of Invention
In the automotive industry, a surface treatment installation intended, for example, for painting bodyworks carried and moved by a conveyor comprises, for example, a set of six machines which are intended to coat the side walls of the bodyworks and a machine, known also as the “overhead machine” intended to coat surfaces which lie roughly horizontally. Each of the six lateral machines is equipped with a sprayer, while the overhead machine comprises three distinct sprayers. Such an installation operates in synchronism with the conveyor transporting the bodyworks. It also has a booth provided with vertical ventilation and with a system for recuperating excess coating product.
The command and control device for such an installation comprises a command and control system common to the entire installation and command and control systems for each of the machines and other elements of the installation.
The command and control system common to all of the sprayers makes it possible in particular to identify the type of bodywork entering the zone of the installation and to track this bodywork until it leaves the zone. It may be pointed out that several bodyworks may lie in the same zone and may be painted at the same time. This system also keeps the installation safe through the various sensors with which it is equipped, and coordinates the operation of the sprayers and the interfaces with the booth, the conveyor, etc.
The command and control systems for each of the machines allow in particular control over the kinematics of the corresponding machine and control over the spraying parameters of the sprayer(s) it supports. The kinematics and the spraying parameters are specific to each bodywork being treated.
A programmable industrial controller may, for example, be associated with each machine or other element of the installation. Each of these controllers is controlled by another programmable industrial controller commanding and controlling the entire operation. This “master” controller is itself connected to a supervisor which may be in the form of a computer of the personal computer type. If several installations are present in one and the same factory, these command and control systems may be organized into a network and a common computer connected to this network is then used for programming the various parameters for each of the installations.
The “master” programmable controller allows information to be received from the various sensors and, through an appropriate means, determines what type of bodywork is arriving in the zone of the installation with which it is associated. This controller has, in memory, for each of the types of bodywork, a table known as the “spraying table” which contains all the orders of positioning of each of the machines and other elements and the setting of each of the sprayers with respect to the advancement of the bodywork along the conveyor. At regular intervals, each interval corresponding, for example, to the movement of the bodywork along the conveyor by a predetermined distance, the machines and sprayers require new settings because the bodywork has made progress through the installation. After each interval of time, the corresponding orders are thus sent to each of the programmable industrial controllers corresponding to a machine or to another element. These controllers are also known as “slave” controllers as opposed to the “master” controller.
The spraying tables for each of the bodywork types are programmed on the computer mentioned earlier used for programming. For a bodywork of given shape, these tables consist in entering, for various positions of the bodywork in the installation, the various orders corresponding, for example, to the positions of the various axes of each machine, to the flow rate of treatment product for each of these sprayers, to the electrical voltage applied, etc. Once the spraying tables have been programmed they are loaded into the “master” controller using disks or the like.
The supervisor for its part allows the progress of the process to be monitored through its various stages and also allows particular orders to be sent to a machine, particularly in the adjustment or maintenance phase. This supervisor has a screen to allow the process to be displayed and a keyboard for inputting orders and/or modifications.
The time needed to optimize these spraying tables for each of the bodyworks is very high. What is actually required is for a great many points to be entered so that the kinematic envelope of each of the machines is close to the shape of the bodywork. This is true for each of the bodyworks and there are generally on average 20 bodyworks at each production factory. As a result, the number of points in the spraying tables is limited to about 100 depending on the complexity of the exterior shape of the bodywork. In addition, bearing in mind the various types of paint, adjustments to the settings of the sprayers are needed. As a result, the number of tables is further multiplied for each of the shades and tables are obtained which, in total, contain of the order of about 10000 programmed points.
In addition, it is necessary to test these tables in real life, that is to say on a bodywork. This test and setting phase may last from a few days to several weeks. It is costly in terms of time and also in terms of operating costs in that it uses up coating and cleaning product and in that it soils the installation and therefore requires maintenance. Furthermore, in car plants, old installations are often replaced with new ones during the summer shutdown period. There are then four weeks in which the old installation has to be taken down, the infrastructures have to be modified, the new installation has to be assembled, commissioned and tested empty and then finally the application has to be set up so that it will be ready to start in full production with the minimum of rejects. The testing and setting phase represents the lengthiest and the most uncertain part of the commissioning of a new installation.
This phase can be shortened in that there now exist means for allowing spraying tables to be simulated prior to the on-site test phase.